1. Field of the Invention
This invention relates broadly to highly fermentable, high maltose, non-crystallizing starch conversion syrups and to methods of producing such syrups. More specifically, the invention concerns an enzymatic method of making and the composition of a starch conversion syrup having high F.E. (fermentable equivalent) values, while reducing or eliminating the need for separation techniques involving crystallization, chromatography, membranes and the like. The syrups of the invention are especially characterized by their high content of maltose and low content of maltotriose (DP3) and higher saccharides.
2. Description of the Prior Art
The basic technology of producing syrups from starch, often referred to as starch conversion syrups, is well known. Commercially, the most important starch conversion syrup is made from corn starch, and hence is called "corn syrup." A substantial demand exists for special corn syrups which are highly fermentable, i.e., have a high F.E. value, preferably greater than about 90 percent.
High F.E. corn syrups are in particular demand as a brewing adjunct by brewers, and especially those brewers making light beers. These syrups generally have higher dextrose content than maltose content. Both dextrose and maltose are totally fermentable; however, dextrose, unlike maltose, produces negative effects on yeast in the brewing process when the dextrose concentration is high which for the purposes of the present invention is greater than 50% (w/w). High concentrations of dextrose are reported to cause decreased viability of the yeast in the fermentation process and to produce objectionable flavors in the finished beer. Therefore, the dextrose content in the present composition is preferred to be 50% or less.
The purpose behind the use of corn syrups with particularly high F.E. values in the brewing of light beers is that virtually all of the sugars contained in the corn syrup are consumed in the fermentation process and leave very little carbohydrate residue behind in the finished beverage. Thus, the calorie content of the "light" beer is less than other beers containing the extra carbohydrate residue.
A number of high maltose syrups are currently available in the marketplace. These syrups generally have a maltose content of 35% or greater. Generally, these syrups have an F.E. of only about 80% or less. Unfortunately, these syrups contain large levels of higher saccharides with a DP (degree of polymerization) greater than DP3. These higher saccharides are resistant to fermentation and consequently these sugars will remain in the finished beer raising the calorie content. Thus, these syrups are unacceptable for producing light beer.
The use of .beta.-amylase enzymes to convert liquified starch to a high maltose syrup is well known. Commercially available syrups made in this manner attain maltose contents of from 35 to 65%. These syrups, however, are generally unacceptable for brewing light beers as they have an F.E. of less than 90%, meaning that at least 10% of the sugars are not fermentable and will remain in the finished beer.
High maltose syrups of about 80% maltose are also presently known in the art. To produce such a high maltose syrup generally requires that either the higher saccharides in the syrup be removed by methods involving chromatographic or membrane separation, or that the maltose be isolated by crystallization. Obviously, these methods entail certain costs and inefficiencies.